1. Field of the Invention
This invention relates to variable-pitch pulley assemblies for use with tension medium strand such as V-belt, which also may include speed sensitive means.
2. Description of the Prior Art
In the prior art, for example, West German Pat. OLS 1802750 shows an expansible pulley having one movable sheave and one fixed sheave on the shaft. The movable sheave is movable relative to the fixed sheave in an axial direction. Both sheaves are secured against rotation relative to one another by means such as a keyway or splines. Each sheave has a running surface for the tension medium strand such as a V-belt which is only partly or semi-circularly looped around the sheaves which produces a tilting or tipping movement which acts upon the keyway or the splines and counteracts the axial displacement. Therefore, the movement of the movable sheave is likely to cause wear on the key or splines.
U.S. Pat. No. 4,010,654 shows a variable-pitch pulley of the foregoing type wherein the foregoing drawbacks are eliminated. Disclosed in this prior art is a V-pulley of variable pitch type which includes two sheaves, at least one of which is displaceable in an axial direction relative to the other, each of the sheaves having a running surface for a V-belt. One of the sheaves is mounted on a shaft-like member with the two systems having means mutually connecting the sheaves to each other and being axially spaced from each other and linked to both sheaves such that one system affords axial displacement of one sheave and the other system is firmly linked to the other sheave. However, two linked portions of the systems are located radially inside with respect to the running surface of the sheaves. As a result, the stroke of each sheave is not sufficient and the pitch of the pulley may not be controlled.